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Message-ID: <1fe9d629-0f5f-4807-b97c-77b3b3c7de72@kaod.org>
Date: Mon, 15 Nov 2021 20:05:17 +0100
From: Cédric Le Goater <clg@...d.org>
To: Marc Zyngier <maz@...nel.org>, <linux-kernel@...r.kernel.org>
CC: Thomas Gleixner <tglx@...utronix.de>,
Michael Ellerman <mpe@...erman.id.au>,
PowerPC <linuxppc-dev@...ts.ozlabs.org>,
Greg Kurz <groug@...d.org>
Subject: Re: [PATCH 16/39] irqdomain: Make normal and nomap irqdomains
exclusive
Hello Mark,
On 5/20/21 18:37, Marc Zyngier wrote:
> Direct mappings are completely exclusive of normal mappings, meaning
> that we can refactor the code slightly so that we can get rid of
> the revmap_direct_max_irq field and use the revmap_size field
> instead, reducing the size of the irqdomain structure.
>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
This patch is breaking the POWER9/POWER10 XIVE driver (these are not
old PPC systems :) on machines sharing the same LSI HW IRQ. For instance,
a linux KVM guest with a virtio-rng and a virtio-balloon device. In that
case, Linux creates two distinct IRQ mappings which can lead to some
unexpected behavior.
A fix to go forward would be to change the XIVE IRQ domain to use a
'Tree' domain for reverse mapping and not the 'No Map' domain mapping.
I will keep you updated for XIVE.
Thanks,
C.
> ---
> include/linux/irqdomain.h | 6 +++---
> kernel/irq/irqdomain.c | 45 ++++++++++++++++++++++++++++++---------
> 2 files changed, 38 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index 723495ec5a2f..0916cf9c6e20 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -149,8 +149,6 @@ struct irq_domain_chip_generic;
> * @parent: Pointer to parent irq_domain to support hierarchy irq_domains
> *
> * Revmap data, used internally by irq_domain
> - * @revmap_direct_max_irq: The largest hwirq that can be set for controllers that
> - * support direct mapping
> * @revmap_size: Size of the linear map table @revmap[]
> * @revmap_tree: Radix map tree for hwirqs that don't fit in the linear map
> * @revmap: Linear table of hwirq->virq reverse mappings
> @@ -173,7 +171,6 @@ struct irq_domain {
>
> /* reverse map data. The linear map gets appended to the irq_domain */
> irq_hw_number_t hwirq_max;
> - unsigned int revmap_direct_max_irq;
> unsigned int revmap_size;
> struct radix_tree_root revmap_tree;
> struct mutex revmap_tree_mutex;
> @@ -207,6 +204,9 @@ enum {
> */
> IRQ_DOMAIN_MSI_NOMASK_QUIRK = (1 << 6),
>
> + /* Irq domain doesn't translate anything */
> + IRQ_DOMAIN_FLAG_NO_MAP = (1 << 7),
> +
> /*
> * Flags starting from IRQ_DOMAIN_FLAG_NONCORE are reserved
> * for implementation specific purposes and ignored by the
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index e0143e640683..fa94c86e47d4 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -146,6 +146,10 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
>
> static atomic_t unknown_domains;
>
> + if (WARN_ON((size && direct_max) ||
> + (!IS_ENABLED(CONFIG_IRQ_DOMAIN_NOMAP) && direct_max)))
> + return NULL;
> +
> domain = kzalloc_node(sizeof(*domain) + (sizeof(unsigned int) * size),
> GFP_KERNEL, of_node_to_nid(to_of_node(fwnode)));
> if (!domain)
> @@ -213,8 +217,14 @@ struct irq_domain *__irq_domain_add(struct fwnode_handle *fwnode, int size,
> domain->ops = ops;
> domain->host_data = host_data;
> domain->hwirq_max = hwirq_max;
> +
> + if (direct_max) {
> + size = direct_max;
> + domain->flags |= IRQ_DOMAIN_FLAG_NO_MAP;
> + }
> +
> domain->revmap_size = size;
> - domain->revmap_direct_max_irq = direct_max;
> +
> irq_domain_check_hierarchy(domain);
>
> mutex_lock(&irq_domain_mutex);
> @@ -482,9 +492,18 @@ struct irq_domain *irq_get_default_host(void)
> return irq_default_domain;
> }
>
> +static bool irq_domain_is_nomap(struct irq_domain *domain)
> +{
> + return IS_ENABLED(CONFIG_IRQ_DOMAIN_NOMAP) &&
> + (domain->flags & IRQ_DOMAIN_FLAG_NO_MAP);
> +}
> +
> static void irq_domain_clear_mapping(struct irq_domain *domain,
> irq_hw_number_t hwirq)
> {
> + if (irq_domain_is_nomap(domain))
> + return;
> +
> if (hwirq < domain->revmap_size) {
> domain->revmap[hwirq] = 0;
> } else {
> @@ -498,6 +517,9 @@ static void irq_domain_set_mapping(struct irq_domain *domain,
> irq_hw_number_t hwirq,
> struct irq_data *irq_data)
> {
> + if (irq_domain_is_nomap(domain))
> + return;
> +
> if (hwirq < domain->revmap_size) {
> domain->revmap[hwirq] = irq_data->irq;
> } else {
> @@ -629,9 +651,9 @@ unsigned int irq_create_direct_mapping(struct irq_domain *domain)
> pr_debug("create_direct virq allocation failed\n");
> return 0;
> }
> - if (virq >= domain->revmap_direct_max_irq) {
> + if (virq >= domain->revmap_size) {
> pr_err("ERROR: no free irqs available below %i maximum\n",
> - domain->revmap_direct_max_irq);
> + domain->revmap_size);
> irq_free_desc(virq);
> return 0;
> }
> @@ -879,10 +901,14 @@ unsigned int irq_find_mapping(struct irq_domain *domain,
> if (domain == NULL)
> return 0;
>
> - if (hwirq < domain->revmap_direct_max_irq) {
> - data = irq_domain_get_irq_data(domain, hwirq);
> - if (data && data->hwirq == hwirq)
> - return hwirq;
> + if (irq_domain_is_nomap(domain)) {
> + if (hwirq < domain->revmap_size) {
> + data = irq_domain_get_irq_data(domain, hwirq);
> + if (data && data->hwirq == hwirq)
> + return hwirq;
> + }
> +
> + return 0;
> }
>
> /* Check if the hwirq is in the linear revmap. */
> @@ -1470,7 +1496,7 @@ static void irq_domain_fix_revmap(struct irq_data *d)
> {
> void __rcu **slot;
>
> - if (d->hwirq < d->domain->revmap_size)
> + if (irq_domain_is_nomap(d->domain) || d->hwirq < d->domain->revmap_size)
> return; /* Not using radix tree. */
>
> /* Fix up the revmap. */
> @@ -1830,8 +1856,7 @@ static void
> irq_domain_debug_show_one(struct seq_file *m, struct irq_domain *d, int ind)
> {
> seq_printf(m, "%*sname: %s\n", ind, "", d->name);
> - seq_printf(m, "%*ssize: %u\n", ind + 1, "",
> - d->revmap_size + d->revmap_direct_max_irq);
> + seq_printf(m, "%*ssize: %u\n", ind + 1, "", d->revmap_size);
> seq_printf(m, "%*smapped: %u\n", ind + 1, "", d->mapcount);
> seq_printf(m, "%*sflags: 0x%08x\n", ind +1 , "", d->flags);
> if (d->ops && d->ops->debug_show)
>
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